Objective: The objective of this study was to investigate the trends in the prevalence and characteristics of unilateral spastic cerebral palsy among children born between 1988 and 2007 in Okinawa, Japan. Method: We conducted a surveillance of children with cerebral palsy using the local cerebral palsy registration system. For analysis purposes, the study was divided into two periods: periodⅠ (from 1988 to 1997) and periodⅡ (from 1998 to 2007). We performed a chi-squared test and Poisson regression analysis. Result: We observed a significant trend for an increased prevalence of unilateral spastic cerebral palsy in periodⅡ (p<0.01). The number of children with unilateral spastic cerebral palsy who were born with birth weights of 1500 g or more and/or a gestational age of 32 weeks or more was increased in periodⅡ. In addition, brain magnetic resonance imaging and computed tomography scans showed that porencephaly and periventricular white matter damage were common findings in preterm children of gestational age less than 31 weeks in period II. The most frequently observed neuroimaging feature in children with a gestational age of over 32 weeks was brain infarction. Conclusion: We found a trend for an increased prevalence of unilateral spastic cerebral palsy in periodⅡ. However, the cause of this increase is as yet unknown.